Basic motion control of a free-swimming biomimetic robot fish

We develop a practical motion control strategy for a radio-controlled, 4-link and free-swimming biomimetic robot fish that uses a flexible posterior body and an oscillating foil as propulsor. Because motion control of robot fish involves hydrodynamics of the fluid medium and dynamics of the robot, it is hard to establish a mathematic model employing purely analytical methods. The fish´s motion control task, based on control performance of the fish, is decomposed into on-line speed control and orientation control. The speed control algorithm is then implemented by using step control, and orientation control is realized by fuzzy logic. Combining with step control and fuzzy control, a point-to-point control algorithm is implemented and applied to the closed-loop experimental system that using a vision-based position sensing subsystem to provide feedback. The running experiments confirm the reliability and effectiveness of the presented algorithms.